JP6286537B2 - Nadir / zenith inertial pointing support for 2-axis gimbal - Google Patents

Description

  Gimbal mounts are often used for accurate line-of-sight (LOS) pointing in systems such as antennas, cameras, telescopes, and turrets. In general, gimbals are support structures that can pivot around one or more axes. For example, a two-axis gimbal system includes two gimbals, each gimbal being configured to rotate about a different orthogonal axis. The outer gimbal is mounted on the base platform and can rotate about an axis through this support point. The inner gimbal is supported by the outer gimbal and can rotate about an axis perpendicular to the axis of rotation of the outer gimbal. Two-axis gimbal systems are often used for LOS pointing and more than higher order gimbal systems because of their ease of operation and low cost.

  However, control problems arise when attempting to point a biaxial gimbal (eg, an elevation zenith gimbal) to elevation + 90 ° (“zenith”) and elevation −90 ° (nadir). In particular, at the zenith and nadir of the gimbal, the LOS is parallel to the azimuth axis of rotation. As a result, the LOS does not move with rotation around the azimuth axis. The loss of this azimuth pointing control is an example of a phenomenon called “gimbal lock”. Azimuth pointing control is further complicated when the gimbal is attached to a movable platform. In particular, the position of the gimbal LOS moves independently of the movement of the gimbal axis due to the movement of the platform. Therefore, the gimbal axis must move in response to the base movement of the platform in order to stabilize the LOS. Control systems have been developed that stabilize the LOS pointing of the two-axis gimbal system at or near the gimbal zenith / nadir, but these control systems still produce significant errors in azimuth pointing control. Therefore, there is a need for an improved system and method for azimuth control in a two-axis gimbal pointing system near the nadir / zenith of the elevation.

  In one embodiment, a method of azimuth pointing for line of sight (LOS) pointing is provided. The method includes: accelerating the movable platform in an inertial frame of the line of sight by movement of the movable platform in a two-axis gimbal having an azimuth gimbal, an elevation gimbal, and a line of sight, and movably coupled to the movable platform; Measuring acceleration of the azimuth gimbal relative to the platform due to movement of the movable platform. The method also includes the step of one or more processors generating a first command signal that is movably coupled to the biaxial gimbal and directs deflection of a biaxial pointing device disposed in the optical path of the line of sight. . The first command signal is based on a measured acceleration of the movable platform and an acceleration rate command representing a target movement relative to the azimuth gimbal. The method also includes measuring a deflection of the biaxial pointing device in the sight inertia frame in response to the first command signal. The method further includes the one or more processors generating a second command signal to command the deflection of the azimuth gimbal based on the deflection of the biaxial pointing device and the measured acceleration of the azimuth gimbal. including.

  In another embodiment, the method may include one or more of the following, alone or in combination. The first and second command signals are generated when the elevation gimbal is oriented at a selected angle. The step of generating the second command signal further includes the step of generating the second command signal based on a relative target movement. The method further includes the step of the one or more processors generating a third command signal that commands deflection of the azimuth gimbal. A third command signal is based on the azimuth gimbal and the second command signal, and when the azimuth gimbal receives the third command signal, the azimuth gimbal is at least part of the deflection of the biaxial pointing device. It moves to correspond to. The method further includes the one or more processors generating an updated relative target motion based on the deflection of the biaxial pointing device and the deflection of the azimuth gimbal in response to the third command signal. Including the steps of: The step of generating the first command signal further comprises the step of converting the acceleration of the movable platform and the target acceleration into a reference frame of the two-axis pointing device. The step of generating the second command signal further includes converting acceleration of the azimuth gimbal into an azimuth gimbal angle in a reference frame of the movable platform, and deflecting the biaxial pointing device to the biaxial pointing device. Converting from a reference frame to a deflection of the biaxial pointing device in the reference frame of the movable platform.

  In another embodiment, an azimuth pointing system that directs line of sight is provided. The pointing system includes a two-axis gimbal movably coupled to a movable platform, including an elevation gimbal, an azimuth gimbal, and a two-axis gimbal that includes a line of sight. The pointing system also includes a two-axis pointing system that is movably coupled to the two-axis gimbal and inserted into the optical path of the line of sight. The pointing system further includes a first sensor adapted to measure the angle and rate of the azimuth gimbal relative to the movable platform. The pointing system also includes a second sensor adapted to measure the inertial movement of the line of sight. The pointing system further includes one or more processors adapted to generate a first command signal and a second command signal. A first command signal commands deflection of the two-axis pointing device, measurement of the acceleration of the movable platform in the inertial frame of the line of sight by movement of the movable platform, measurement of the second sensor, and the azimuth gimbal And an acceleration rate command representing the target movement relative to. A second command signal commands deflection of the azimuth gimbal and acceleration of the azimuth gimbal relative to the movable platform due to deflection of the two-axis pointing device in response to the first command signal and movement of the movable platform Based on the measurement by the first sensor.

  In another embodiment, the pointing system may include one or more of the following, alone or in combination. The one or more processors are further adapted to generate the second command signal based on the rate command. The one or more processors are further configured to generate a third command signal that commands deflection of the azimuth gimbal, based on the acceleration of the azimuth gimbal and the second command signal. Have been adapted. The biaxial pointing device comprises a light beam steering device adapted to steer the line of sight about two rotational axes.

  In one embodiment, a non-transitory computer readable medium incorporating computer readable program code for comparing decision options is provided. The computer readable program includes instructions that, when executed by a processor, have two axes movably coupled to a movable platform having an azimuth gimbal, an elevation gimbal, and a line of sight on the processor. In the gimbal, the acceleration of the movable platform in the gaze inertial frame due to the movement of the movable platform relative to the platform and the acceleration of the azimuth gimbal due to the movement of the movable platform is measured, and is movably coupled to the two-axis gimbal; A first command signal commanding deflection of a biaxial pointing device disposed in the optical path of the line of sight, the first command signal being based on a measured acceleration of the movable platform and a target movement relative to the azimuth gimbal Frames And the deflection of the biaxial pointing device is measured in the gaze inertia frame in response to the first command signal, the deflection of the biaxial pointing device and the measured acceleration of the azimuth gimbal. And generating a second command signal for instructing the deflection of the azimuth gimbal.

  In other embodiments, the computer-readable medium further includes one or more instructions that, when executed, cause the processor to execute one or more of the following. A second command signal is generated based on the relative target movement. Based on the measured acceleration of the azimuth gimbal and the second command signal, a third command signal is generated that commands deflection of the azimuth gimbal. In response to a third command signal, an updated acceleration command is generated to command deflection of the azimuth gimbal based on the deflection of the biaxial pointing device and the deflection of the azimuth gimbal. The acceleration of the azimuth gimbal is converted into an azimuth gimbal angle at the reference frame of the movable platform, and the deflection of the two-axis pointing device is changed from the reference frame of the two-axis pointing device to the two-axis pointing at the reference frame of the movable platform. Convert to device deflection.

These and other objects, features and advantages will become apparent from a more specific description of the embodiments illustrated in the accompanying drawings. In the different drawings, the same reference numbers refer to the same parts. The drawings are not necessarily to scale, and some are emphasized in illustrating the principles of the embodiments.
It is a figure which shows one Embodiment of a biaxial gimbal pointing system. FIGS. 2A-2D are diagrams illustrating a gimbal that is directed toward line of sight (LOS) pointing when the gimbal elevation moves toward the zenith / nadir. 3A and 3B are diagrams illustrating the near-nadir motion of one embodiment of a two-axis pointing device used for line-of-sight stabilization in a pointing system. 4A and 4B are diagrams illustrating near-nadir motion of a pointing system of the present disclosure that utilizes both a biaxial pointing device and a gimbal set to stabilize line of sight. It is a figure which shows one Embodiment of the control system for nominal azimuth | direction pointing out of a near nadir area. It is a figure which shows one Embodiment of the control system for near nadir azimuth pointing.

  When a two-axis gimbal pointing device is attached to a vehicle such as an aircraft, the outer gimbal is generally oriented with a rotational axis extending parallel to the yaw axis, and the inner gimbal is generally Oriented with a rotation axis perpendicular to the rotation axis of the outer gimbal. When oriented in this manner, the outer gimbal provides rotation in the azimuth direction (ie, in-plane rotation) and the inner gimbal provides rotation in the elevation direction (ie, out-of-plane rotation).

  The biaxial gimbal uses an inertial sensor to stabilize the LOS with respect to moving moving means. That is, in order to accurately point the LOS to the desired target, the commands sent to the azimuth and elevation of the gimbal are required to direct the LOS to the desired target and are independent of the movement of the moving means. And the movement of the moving means must be considered. For example, in response to the base movement of the platform, the LOS movement due to the base movement is measured by an inertial sensor, and the gimbal support is adjusted based on feedback from the inertial sensor to maintain a constant LOS. May be.

  However, the azimuth axis performance of the biaxial gimbal deteriorates as the elevation deviates from 0 °. Consider the example shown in FIG. 2A. FIG. 2A shows a spherical coordinate system superimposed on the Cartesian axes (x, y, z). The z-axis functions as the azimuth (Az) rotation axis of the biaxial gimbal, and the y-axis functions as the elevation (El) rotation axis of the biaxial gimbal. The LOS is directed based on movement about the respective axes of the Az and El gimbals.

  In moving means such as an aircraft, body pitch and roll acceleration are linked to LOS due to elevation limitations. When pointing towards a goal of 0 ° elevation (eg, goal 122) (FIG. 2B), the LOS inertial sensor allows the freedom of movement in El, regardless of elevation, of the elevation axis. Aligned with bearing and motor (elevation control authority axis). In contrast, the LOS inertial sensor is only aligned with the azimuth axis (control authority axis) with a 0 ° declination. As a result, there is no coupling with the elevation axis due to the base motion at any declination, but there is no coupling with the azimuth axis due to the base motion only at the declination 0 °.

  As the elevation declination follows the target 122 and increases from 0 °, the azimuth control authority axis and the azimuth inertial feedback axis become misaligned (FIG. 2C). For example, at an angle of 45 °, 71% of aircraft body roll motion is associated with LOS when viewed from the front or back of the aircraft. From either wing's perspective, 71% of aircraft body pitch motion is linked. Furthermore, only 71% of the azimuth control authority axis motion is tied to the azimuth feedback sensor axis. As the depression angle increases, the loss of control authority coupling in azimuth and aircraft body roll and pitch disturbances continue to increase. The signal-to-noise ratio (SNR) of azimuth inertia rate feedback deteriorates as the declination increases.

  As the declination increases, the SNR deteriorates to the point where coordinate frame switching is necessary to maintain azimuth gimbal axis control. For example, the feedback sense for azimuth control is switched from the LOS inertial sensor to the aircraft body reference frame sensor, resulting in a loss of inertia reference frame line of sight control. When the target reaches the gimbal nadir / azimuth, the azimuth inertial feedback axis and the bearing / motor pair are orthogonal (FIG. 2D). In this position, azimuth pointing control is completely lost. This is because the rotation around the azimuth axis does not change the LOS pointing direction (“gimbal lock”).

  If the inertial pointing control is lost when approaching the gimbal nadir / zenith, a large error occurs in the pointing control. As a result, there is a spatial volume (eg, conical volume) centered around the gimbal nadir / zenith where azimuth pointing control is very limited.

  To solve the gimbal nadir / near-pointing problem, a two-axis gimbal system was developed that included a two-axis beam steering mirror inserted into the optical path of the imaging sensor or beam director. This mirror is sometimes called a fast steering mirror (FSM). This is because the response is several times faster than the conventional mass stabilized gimbal shaft. The FSM is coupled to a biaxial gimbal, oriented by a gimbal set, and moved with a LOS (“Gimbal LOS”). As shown in FIG. 3A, the FSM is aligned with both the elevation and azimuth gimbal axes and can be deflected in two directions independently of the gimbal set (“FSM deflection”). The LOS inertial sensor may be mounted on the FSM.

  In the gimbal zenith / nadir region, the inertial pointing of the azimuth gimbal is lost, so LOS pointing is controlled by the FSM deflection alone, without the assistance of the gimbal set. The net LOS is therefore the sum of the gimbal LOS due to the gimbal motion approaching the gimbal zenith / nadir region and the control of the FSM deflection in the near zenith / nadir region. For example, the residual error, i.e., the difference between the gimbal LOS position and the desired LOS position (e.g., the target position) may be provided as a command to control the FSM deflection. When viewed in terms of azimuth (FIG. 3B), the FSM moves relative to the gimbal LOS to implement a net LOS.

  However, this solution does not completely solve the azimuth pointing control problem. In the vicinity of the gimbal zenith / nadir, the FSM has full control of LOS pointing and without the help of the gimbal set. The FSM has a finite deflection range, and when trying to stabilize the LOS, the base movement of the moving means may hit a mechanical stop. As a result, when certain base movements (eg, relatively large base movements) occur, the FSM cannot fully perform the desired pointing commands due to these mechanical constraints, resulting in LOS Stabilization may not work.

  Embodiments of the present disclosure relate to a control system and methodology for improved azimuth pointing control in a two-axis gimbal system. For example, the disclosed embodiments can recover azimuth inertial pointing in near nadir elevation. Under certain conditions, inertial pointing can be recovered near the nadir.

  The improved pointing system may include a two-axis elevation azimuth gimbal mounted on a movable platform (eg, a moving means such as an aircraft, land vehicle, underwater moving means, etc.). A two-axis pointing device, such as a high-speed steering mirror (FSM), is further provided and can be deflected about two axes independently of the gimbal set. The system may further include a sensor adapted to measure movement of the 2-axis gimbal and the 2-axis pointing device. For example, the sensor may include an inertial sensor that measures eye movement relative to the movable platform. The sensors may include rate sensors and angle sensors that measure the movement of the azimuth gimbal relative to the movable platform. The pointing system may further include a plurality of processors in communication with the sensors and motors of the 2-axis gimbal and 2-axis pointing device, respectively. Multiple processors can generate commands to move the 2-axis gimbal and 2-axis pointing device. In one embodiment, the improved pointing system may implement a control process that utilizes feedback from a two-axis pointing device to restore inertial pointing control to the azimuth gimbal. 4A-4B show the FSM deflection with respect to neutral position (gimbal LOS position) and mechanical range. As the biaxial pointing device moves (FIG. 4A), the deflection of the biaxial pointing device can be used as a command to move the gimbal set. That is, the gimbal set may “follow” the FSM deflection to move the gimbal LOS as close as possible to the net LOS realized by the FSM. This process of controlling the gimbal set in the near nadir region effectively returns the inertial pointing control to the gimbal set because the gimbal set moves relative to the FSM deflection and the movement of the FSM is inertial controlled.

  This coordinated movement of the biaxial pointing device with the gimbal set also has the advantage of limiting the biaxial pointing device so that it does not reach the mechanical limits that limit its range of motion. As the gimbal LOS moves toward the net LOS position (FIG. 4B), the FSM moves closer to its center or neutral position, from which the FSM can move its maximum travel distance. As a result, the FSM can accommodate larger base motion disturbances when the FSM is located near the mechanical limit, improving the stabilization capability of the FSM.

  Furthermore, embodiments of the present disclosure may just inertia point the nadir if the base movement of the moving means is limited. For example, as long as the LOS inertial deflection stays within the FSM field of relegation, inertial pointing is maintained even if the gimbal set does not follow movement.

  For clarity, embodiments of the present disclosure may be described with respect to nadir and near nadir elevation. However, it will be appreciated that such references may be applied to zenith and near zenith elevations as needed.

  Returning now to FIG. FIG. 1 schematically illustrates one embodiment of a pointing system 100 of the present disclosure. System 100 includes a two-axis gimbal 104, a two-axis pointing device 112, and a control system 116. As will be described in more detail later, the motion of the biaxial gimbal 104 and the biaxial pointing device 112 is issued from a control system 116 that directs the LOS of the imaging device 114 in a desired direction (eg, in the direction of the target position 122). It may be controlled by a command.

  In a preferred embodiment, the imaging device 114 is an optical imaging device such as a still image or video camera. In another embodiment, the imaging device 114 is an electro-optic transmitter (eg, a laser). However, embodiments of the present disclosure may be adapted for use with any electro-optic transmitter or receiver, alone or in combination, as desired.

  In some embodiments, the platform 102 may be any structure on which the biaxial gimbal 104 can be mounted. In some embodiments, platform 102 is a movable platform such as a moving means (eg, land vehicle, aqueous moving means, aircraft, etc.). In another embodiment, platform 102 may be a stationary platform.

  The biaxial gimbal 104 may include two gimbals, one mounted on the other and having orthogonal pivot axes. If the horizontal plane is the reference plane, the first gimbal may be oriented in a direction whose rotation axis is perpendicular to the reference plane (referred to as azimuth gimbal 106). The second gimbal may be oriented in a direction perpendicular to the azimuth gimbal 106 (referred to as an elevation gimbal 110). For example, as shown in FIG. 1, the elevation gimbal 110 may be mounted on the azimuth gimbal 106. However, in other embodiments, any two axis gimbal may be utilized. The biaxial gimbal 104 may be directly coupled (eg, kinematically coupled) to the platform 102 via the azimuth gimbal 106. The imaging device 114 may also be coupled to a two-axis gimbal 104 that directs the LOS axis of the imaging device.

  The biaxial pointing device 112 is a device that allows further steering of the LOS of the imaging device 114 by movement along the two axes and is independent of the biaxial gimbal 104. For example, a plurality of mirrors, lenses, or other beam steering devices (not shown) may be utilized to direct the LOS from the imaging device 114 to the two-axis pointing device 112. In general, the biaxial pointing device is a beam steering device that can move relatively faster than the biaxial gimbal 104. In some embodiments, the biaxial pointing device 112 is a fast steering mirror (FSM). For example, the biaxial pointing device 112 may include a first mirror that is normally mounted parallel to a flat base so that the first mirror can pivot about a center point near its surface. An actuator may be mounted on a pair of vertical axes between the mirror and the edge of the base. The actuator pair may be driven with a push-pull motion that rotates the mirror about two orthogonal axes to allow a two-axis angular scan. In another embodiment, the biaxial pointing device may be any type of light beam steering device, for example a beam steering device by refraction or reflection. The control system 116 may include multiple processors that communicate with multiple sensors. Examples of sensors may include, but are not limited to, a rate and angle sensor 102A referenced to the platform and LOS inertial sensor 104A. The rate and angle sensor 102A may provide a rate and angle measurement of the azimuth gimbal 106 relative to the platform 102. For example, the rate and angle sensor 102A may be a rate detecting tachometer and an angle detecting resolver or encoder. The LOS inertial sensor 104A may be a two-axis gyroscope or two one-axis gyroscopes mounted on a lens in the LOS optical path. The sensors 102A, 104A may further be adapted to output a signal representative of the detected motion to the control system 116.

  The control system 116 may communicate with the 2-axis gimbal 104, the 2-axis pointing device 112, and the command calculation device 124. As will be described in more detail below, the pointing system 100, relative to the biaxial gimbal 104 and platform 102, when mounted on the moving platform 102, continues to point the LOS 120 to the target 122. It must move to correspond to the unmoving motion and any relative movement of the target 122.

  The control system 116 may receive commands from a command calculation device 124 that commands the movement of the biaxial gimbal 104 to follow the relative movement of the target 122 relative to the biaxial gimbal. However, commands from the command computing device 124 do not take into account the base motion of the moving platform 102. Thus, the control system 116 may further receive feedback from the sensors 102A, 104A that reflects the underlying motion of the platform 102. The control system 116 may generate new commands for movement of the two-axis gimbal 104 and the two-axis pointing device 112 using both commands received from the command calculation device 124 and feedback from the sensors 102A, 104A. Good.

  Reference is now made to FIG. FIG. 5 is a schematic diagram illustrating a control process 500 implemented by the control system 116 for azimuth pointing of the system 100 when the elevation gimbal 110 deflection is outside the nadir / near nadir region. For example, in one embodiment, the control process 500 may be used where the elevation deflection is less than about 60 °, preferably less than about 80 °. However, it will be appreciated that the exact range of elevation gimbal deflection in which the control process 500 is performed is reflected in the servo adjustment of the implementation of the pointing system 100 as reflected in the signal to noise ratio (SNR) of the azimuth inertial rate feedback. Dependent. Accordingly, those skilled in the art may use process 500 to determine the acceptable range of SNR for azimuth pointing control for each deployment.

  The control process 500 may utilize a LOS inertial sensor 104A that measures the base motion of the platform 102 relative to the gimbal LOS 120. The control process 500 also receives as input a command representing relative target movement from the command computing device 124. The movement of the azimuth gimbal 106 provides a relatively coarse stability of the LOS 120, and the movement of the biaxial pointing device 112 provides a relatively fine stability of the LOS 120.

  For clarity of explanation, process 500 is labeled with operations 501-507. However, it will be appreciated that the control process 500 is a continuous process performed by the control system 116 and is not limited to a particular starting point or ending point.

  In operation 501, a base motion acceleration of the platform 102 occurs. In operation 502, the base motion acceleration of the platform 102 is coupled to the LOS inertial sensor 104A through a two-axis gimbal 104 kinematically mounted on the platform 102. These base motions torque the LOS inertial sensor 104A of the LOS 120 inertial reference frame, causing image instability. In operation 503, LOS inertial sensor 104 </ b> A observes the combined base motion acceleration in azimuth feedback sensing for gimbal LOS 120.

  The control processor 116A further receives a signal from a command calculation system 124 that commands the movement of the azimuth gimbal 104 to follow the movement of the target 122 relative to the two-axis gimbal 104 and the platform 102. For example, the signal from the command calculation system 124 may include an angular velocity command for the desired sensor's line of sight pan rate. Based on the sensed inertia rate and angular velocity commands, the control processor 116A may generate separate commands for the movement of the azimuth gimbal 106 and the biaxial pointing device 112. To generate a motion command for each of the azimuth gimbal 106 and the two-axis pointing device 112, the first control processor 116A, in operation 504, measures the inertia rate and angular velocity commands measured along the feedback sensing axis of the LOS inertial sensor 104A. Inertial error signals are generated. The inertia error signal represents the difference between the current measured angular velocity of the gimbal LOS 120 and the desired angular velocity of the gimbal LOS 120. Another command may be provided to both the azimuth gimbal 106 and the biaxial pointing device 112 to minimize the inertial error signal. By minimizing the inertia error signal, the difference between the desired LOS and the actual LOS is made as small as possible.

  In operation 504A, commands for movement of the azimuth gimbal 106 are generated by the control processor 116A and provided to the azimuth motor and amplifier in communication with the azimuth gimbal 106. In order to generate the azimuth motor torque command, the control processor 116A applies predetermined control rules to minimize the inertia error signal. For example, the control rule may be proportional plus integral control. In response to the received torque command, the azimuth motor and amplifier move the azimuth gimbal 106 along the control authority axis to minimize the inertia rate error. The remaining residual rate error represents the coarse stabilization performance of the control system 116.

  In operations 506, 506A, commands for movement of the two-axis pointing system 112 are generated. In operation 506, the control processor 116A integrates the coarse inertia rate error signal and sends this signal to the second control processor 116B. However, it is not appropriate for the integrated rate error signal to be used as an input command for the movement of the biaxial pointing device. Accordingly, in operation 506A, the control processor 116B operates on the received integrated rate error to generate a command suitable for the 2-axis pointing system 112 and output a command for the 2-axis pointing device 112. For example, the effect on the integrated rate error may include phase and amplitude correction and rotation of the biaxial pointing device 112 to the reference frame.

  Command output by the control processor 116B is received by the two-axis pointing device 112. In one embodiment, the biaxial pointing device 112 may be a biaxial fast steering mirror inserted in the optical path of the imaging device 114. In response to the received command, the two-axis pointing device 112 dynamically steers the optical axis of the imaging device 114 in the opposite direction by a magnitude approximately equal to the integrated inertia rate error, resulting in a LOS inertia error. May be further reduced (operation 507). The remaining residual rate error represents the fine stabilization performance of the pointing system 100.

  The combination of the coarse LOS stabilization provided by the azimuth gimbal 106 and the fine LOS stabilization provided by the two-axis pointing device 112, represented in FIG. 5 by the symbol Σ, represents the final LOS position after one control loop. Although the control process 500 has been described with respect to sequential operation, it will be appreciated that the coarse control loop (operations 501-505) and the fine control loop (operations 506-507) may be performed sequentially and simultaneously for LOS position control. Good.

  Reference is now made to FIG. FIG. 5 is a schematic diagram illustrating a control process 600 implemented by the control system 116 for azimuth pointing of the system 100 when the elevation gimbal 110 deflection is inside the nadir / near nadir region. As described above, the control process 600 operates to control the azimuth gimbal 106 and the biaxial pointing device 112 for LOS pointing. However, since the LOS inertial control of the azimuth gimbal 106 in nadir / near nadir deflection is difficult, the control process 600 uses the LOS inertial sensor 104A for the pointing control of the two-axis pointing device 112, and the LOS inertial pointing control is performed. Can be maintained. However, if the degree of movement of the biaxial pointing device 112 is limited, the control of the LOS 120 pointing by the biaxial pointing device 112 alone will cause the biaxial pointing device 112 to reach its mechanical limit and move completely in the desired direction. Absent.

  To avoid this difficulty, the process 600 may also utilize the output deflection of the biaxial pointing device 112 to further steer the azimuth gimbal 106 to follow the biaxial pointing device 112. Since the range of motion of the azimuth gimbal 106 is much greater than that of the two-axis pointing device 112, this movement of the azimuth gimbal 106 prevents the two-axis pointing device 112 from reaching its mechanical limits.

  In one embodiment, the control process 600 may be used with elevation deflections of 60 ° or more, 70 ° or more, 80 ° or more, and the like. However, as described above, the specific implementation of the pointing system 100 is such that the exact range of elevation gimbal deflection in which the control process 600 is performed is reflected in the signal-to-noise ratio (SNR) of the azimuth inertial rate feedback. You may depend on the servo adjustment. Accordingly, those skilled in the art may determine an unacceptable range of SNR for azimuth pointing control using process 500 instead of using control process 600 in this manner for each deployment.

  For clarity of explanation, process 600 is labeled with operations 601-607. However, it will be appreciated that the control process 600 is a continuous process performed by the control system 116 and is not limited to a particular starting point or ending point.

  Here, the control of the movement of the biaxial pointing device 112 will be described with reference to operations 601-603 and 606-607. In operations 601 and 602, base motion acceleration of the platform 102 occurs during the motion of the platform 102, similar to the operations 501 and 502 described above. The base motion acceleration of the platform 102 is coupled to the LOS inertial sensor 104A through a two-axis gimbal 104 mounted kinematically on the platform 102. These base motions torque the LOS inertial sensor 104A of the LOS 120 inertial reference frame, causing image instability. The LOS inertial sensor 104A measures the combined base motion acceleration in the azimuth feedback sensing axis that represents the acceleration of the moving platform 102 in the LOS inertia frame due to the movement of the movable platform 102.

  In operation 603, the LOS inertial sensor 104A further outputs a signal representative of the measured acceleration. However, in contrast to the process 500, the inertia rate measured by the LOS 120 inertial sensor 104A is received by a third control processor 116C communicating with the two-axis pointing device 112, rather than the control processor 116A communicating with the azimuth gimbal. The control processor 116C receives from the command calculation system 124 a signal (e.g., an angular velocity command) that commands the biaxial gimbal 104 to move the pointing system 100 to follow the movement of the target 122. For example, the signal from the command calculation system 124 may include an angular velocity command for the desired sensor's line of sight pan rate.

  In operation 606, the control processor 116C generates a command signal instructing the deflection of the biaxial pointing device 112 and outputs the command to the biaxial pointing device 112. The command signal is based on the measured acceleration of the movable platform 102 received from the LOS inertial sensor 104 </ b> A and the target's relative motion with respect to the biaxial gimbal 104. For example, the control processor 116C generates an inertia error signal by taking the difference between the angular velocity command and the inertia rate measured along the feedback detection axis of the LOS inertial sensor 104A. The inertial error signal represents the difference between the measured current angular velocity of communication with the biaxial pointing device 112 and the desired angular velocity of the biaxial pointing device 112. By moving the biaxial pointing device 112 to minimize the inertial error signal, the difference between the desired LOS and the actual LOS is made as small as possible.

  As described with reference to operation 506A, the control processor 116C may integrate the inertia error and operate based on the integrated inertia error to generate a command suitable for the two-axis pointing system 112. For example, operations may include phase and amplitude correction and rotation of the biaxial pointing device 112 to a reference frame.

  Command output by the control processor 116C is received by the biaxial pointing device 112. In one embodiment, the biaxial pointing device 112 may be a biaxial fast steering mirror inserted in the optical path of the imaging device 114. In response to the received command, the two-axis pointing device 112 dynamically steers the optical axis of the imaging device 114 in the opposite direction by a magnitude approximately equal to the integrated inertia rate error, resulting in a LOS inertia error. May be further reduced (operation 607). The remaining residual rate error represents the stabilizing performance of the biaxial pointing system 112.

  The control of the movement of the azimuth gimbal 106 will now be described with reference to operations 601-605. In operations 601 and 602, base motion acceleration of the platform 102 occurs during the motion of the platform 102, similar to the operations 501 and 502 described above. The base motion acceleration of the platform 102 is coupled to the rate and angle sensor 102A. The rate and angle sensor 102A measures the acceleration of the azimuth gimbal relative to the platform 102 due to the movement of the movable platform. The sensor 102A further outputs the detected gimbal rate and the gimbal position calculated from the measured motion of the azimuth gimbal 106 relative to the platform 102. The gimbal position may be provided to the control processor 116D and the gimbal rate may be provided to the control processor 116E.

  In operation 604A, the control processor 116D may generate an azimuth rate command and output the azimuth rate command to the control processor 116E. The azimuth rate command may be based on biaxial pointing device deflection and gimbal angle feedback. The rate command may command the movement of the azimuth gimbal 106 to correspond to the deflection of the biaxial pointing device 112. As a result, the process 600 may prevent the biaxial pointing device from reaching the mechanical limit.

  The rate command output by control processor 116D may be further modified by the angular velocity command output by command calculation system 124 prior to receipt by control processor 116E (operation 604B). That is, the command input to the azimuth gimbal 106 may be based on the relative movement of the target 122 relative to the azimuth gimbal 106 and the deflection of the biaxial pointing device 112. This composite command is an input to the control processor 116E and has the advantage of moving the azimuth gimbal 106 taking into account both the movement of the biaxial pointing device 112 and the target movement.

  In operation 604B, commands for movement of the azimuth gimbal 106 are generated by the control processor 116E and provided to the azimuth motor and amplifier in communication with the azimuth gimbal 106. As described above, the control processor 116E receives both the composite command signal and the gimbal rate feedback. To generate the azimuth motor torque command, the control processor 116E takes the difference between the composite rate command and the gimbal rate feedback to determine an error signal and further applies a predetermined control rule to minimize the error signal. For example, the control rule may be proportional plus integral control. In response to the received torque command, the azimuth motor and amplifier move the azimuth gimbal 106 along the control authority axis to minimize the inertia rate error and maximize the mechanical movement of the two-axis pointing device 112 (operation 605). . The remaining residual rate error represents the stabilization performance of the azimuth gimbal 106.

  The combination of LOS stabilization provided by the azimuth gimbal 106 and the biaxial pointing device 112, represented by the symbol Σ in FIG. 6, represents the final LOS position after one control loop. Although the control process 600 has been described with respect to sequential operation, it will be appreciated that the control of the azimuth gimbal 106 and the two-axis pointing device 112 may be performed sequentially and simultaneously for LOS position control.

  The systems and methods described above can be implemented with digital electronic circuitry, computer hardware, firmware, and / or software. Implementation is also possible as a computer program product. Implementation can also be performed, for example, on a machine readable storage device that is executed by or controls the operation of a data processing apparatus. An implementation may be, for example, a programmable processor, a computer, and / or multiple computers.

  A computer program can be written in any form of programming language, including a compiler and / or interpreter language. Computer programs can be deployed in any form, including stand-alone programs or subroutines, elements, and / or other units used in a computing environment. The computer program can be executed on one computer or expanded to be executed on a plurality of computers in one place.

  The method steps may be performed by one or more programmable processors that execute the functions of the present invention by executing a computer program and operating on input data to produce output. The method steps can be performed by application specific logic and the device can also be implemented as application specific logic. The circuit may be, for example, an FPGA (Field Programmable Gate Array) and / or an ASIC (Application Specific Integrated Circuit). Subroutines and software agents may refer to portions of computer programs, processors, special circuits, software, and / or hardware that implement the functions.

  Processors suitable for executing computer programs include, for example, both special purpose and general purpose microprocessors and any one or more processors of any type of digital computer. Generally, a processor will receive instructions and / or data from a read-only memory or a random access memory. The essential elements of a computer are a processor that executes instructions and one or more memory devices that store instructions and data. Generally, a computer includes one or more large-scale storage devices (eg, magnetic disks, magneto-optical disks, or optical disks, etc.) that store data, and operate to receive data from and / or send data to it They may be combined as possible.

  Data transmission and commanding can also take place via a communication network. Information carriers suitable for utilizing computer program instructions and data include all forms of non-volatile memory including, for example, semiconductor memory devices. The information carrier can be, for example, an EPROM, EEPROM, flash memory device, magnetic disk, internal hard disk, removable disk, magneto-optical disk, CD-ROM, and / or DVD-ROM disk. The processor and memory may be supplemented by and / or incorporated with application specific logic.

  In order to provide user interaction, the above approach can be implemented on a computer having a display device. The display device may be, for example, a cathode ray tube (CRT) and / or a liquid crystal display (LCD) monitor. The user interaction can be, for example, a display of information to the user and a keyboard and pointing device (eg, a mouse or trackball) that allows the user to input to the computer (eg, interact with user interface elements). . Other types of devices can also be used to provide user interaction. Other devices may be feedback provided to the user, for example, in any form of sensory feedback (eg, visual feedback, audio feedback, tactile feedback, etc.). Input from the user can be received in any form including, for example, acoustic, speech, and / or tactile input.

  The above approach may be implemented in a distributed computing system that includes a backend component. The backend component may be, for example, a data server, a middleware component, and / or an application server. The above approach may also be implemented in a distributed computing system that includes a front-end component. The front-end component can be, for example, a client computer having a graphical user interface, a web browser that allows the user to interact with the implementation, and / or other graphical user interfaces for the sending device. The components of the system can be interconnected by any form or medium of digital data communication (eg, a communication network). Examples of communication networks include a local area network (LAN), a wide area network (WAN), the Internet, a wired network, and / or a wireless network.

  The system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship between the client and the server is generated by a computer program that is executed on each computer and has a client-server relationship with each other.

  The packet-based network includes, for example, the Internet, a carrier Internet protocol (IP) network (for example, a local area network (LAN), a wide area network (WAN), a campus area network (CAN), a metropolitan area network (MAN), and a home area. Network (HAN)), private IP network, IP private branch exchange (IPBX), wireless network (eg, radio access network (RAN), 802.11 network, 802.16 network, general packet radio service (GPRS) network, HiperLAN ), And / or other packet-based networks. Circuit-based networks include, for example, public switched telephone networks (PSTN), private branch exchanges (PBX), wireless networks (eg, RAN, Bluetooth®, code division multiple access (CDMA) networks, time division multiple access (TDMA). ) Network, Global System for Mobile Communications (GSM® network), and / or other circuit-based networks.

  The sending device can be, for example, a computer, a computer with a browser device, a telephone, an IP phone, a portable device (eg, a cellular phone, a personal digital assistant (PDA) device, a laptop computer, an email device), and / or other communication device Can be included. The browser device is, for example, a computer having a world wide web browser (for example, Microsoft (registered trademark) Internet Explorer (registered trademark) issued by Microsoft, Mozilla (registered trademark) Firefox issued by Mozilla), or the like. For example, it may include a desktop computer, a laptop computer). The portable computing device includes, for example, Blackberry (registered trademark).

  “Comprise”, “include”, and / or their plural forms are open-ended and include those that are listed and may include those that are not. “And / or” is open-ended and includes one or more of the listed and combinations of the listed.

  It will be appreciated by persons skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or basic characteristics thereof. The above embodiments should be considered as illustrative in all points and not restrictive of the invention described herein. The scope of the present invention is described not by the above description but by the appended claims, and all changes that come within the meaning and range of equivalency of the claims are embraced therein.

Claims (16)

A method of azimuth pointing of gaze,
In a two-axis gimbal having an azimuth gimbal, an elevation gimbal, and a line of sight and movably coupled to a movable platform,
Acceleration of the movable platform in the gaze inertial reference frame by movement of the movable platform;
Measuring the acceleration of the azimuth gimbal relative to the movable platform due to movement of the movable platform;
A first command signal movably coupled to the two-axis gimbal and commanding a deflection of a two-axis pointing device disposed in the optical path of the line of sight, the measured acceleration of the movable platform If the steps of generating a first command signal based on the relative target dynamic way back for the azimuth gimbal,
Measuring a deflection of the biaxial pointing device in response to the first command signal in an inertial reference frame of the line of sight;
And wherein the one or more processors generate a second command signal that commands deflection of the azimuth gimbal based on the deflection of the biaxial pointing device and the measured acceleration of the azimuth gimbal. . The method of claim 1 , wherein the first command signal and the second command signal are generated when the elevation gimbal is oriented at a selected angle.   The method of claim 1, wherein generating the second command signal further comprises generating the second command signal based on relative target movement.   The one or more processors further comprising generating a third command signal that commands deflection of the azimuth gimbal based on the azimuth gimbal and the second command signal; The method of claim 1, wherein when the azimuth gimbal receives the third command signal, the azimuth gimbal moves to correspond to at least a portion of the deflection of the two-axis pointing device.   The one or more processors further comprising generating an updated relative target motion based on the deflection of the biaxial pointing device and the deflection of the azimuth gimbal in response to the third command signal; The method of claim 4.   The method of claim 1, wherein generating the first command signal further comprises converting the acceleration of the movable platform and the acceleration of the target into a reference frame of the two-axis pointing device. .   The step of generating the second command signal further includes converting acceleration of the azimuth gimbal into an azimuth gimbal angle in a reference frame of the movable platform, and deflecting the biaxial pointing device to the biaxial pointing device. Converting from a reference frame to a deflection of the biaxial pointing device in a reference frame of the movable platform. A biaxial gimbal movably coupled to a movable platform, including an elevation gimbal, an azimuth gimbal, and a line of sight;
A biaxial pointing device movably coupled to the biaxial gimbal and inserted into the optical path of the line of sight;
A first sensor adapted to measure the angle and rate of the azimuth gimbal relative to the movable platform;
A second sensor adapted to measure inertial movement of the line of sight;
One or more processors,
A first command signal commanding deflection of the biaxial pointing device, wherein the second sensor measures the acceleration of the movable platform in an inertial reference frame of the line of sight due to movement of the movable platform; a first command signal based on the relative target dynamic way back against the azimuth gimbal,
A second command signal commanding deflection of the azimuth gimbal, the deflection of the two-axis pointing device in response to the first command signal, and the movement of the movable platform, and the movement of the movable platform of the azimuth gimbal One or more processors adapted to generate a second command signal based on a measurement of acceleration by the first sensor.
Azimuth pointing system. The system of claim 8, wherein the one or more processors are further adapted to generate the second command signal based on a target movement relative to the azimuth gimbal .   The one or more processors are further configured to generate a third command signal that commands deflection of the azimuth gimbal, based on the acceleration of the azimuth gimbal and the second command signal. The system of claim 9, wherein the system is adapted. The biaxial pointing device comprises a light beam steering device adapted to steer the line of sight about two rotational axes;
The system according to claim 8. To the processor,
In a two-axis gimbal having an azimuth gimbal, an elevation gimbal, and a line of sight and movably coupled to the movable platform, the movement of the movable platform causes the acceleration of the movable platform in the inertial reference frame of the line of sight, and the movement Measuring acceleration of the azimuth gimbal relative to the movable platform due to platform movement;
A first command signal movably coupled to the two-axis gimbal and commanding a deflection of a two-axis pointing device disposed in the optical path of the line of sight, the measured command of the movable platform and the azimuth gimbal Generating a first command based on relative target movement;
The deflection of the two-axis pointing device in response to said first command signal, and measuring for the inertial reference frame of the sight,
A deflection of the two-axis pointing device, the based on the measured acceleration of the azimuth gimbal, the azimuth gimbal second command signal computer program for executing the steps of generating for commanding deflection. The computer program causes the processor to generate the second command signal based on the relative target movement.
The computer program according to claim 12. The computer program causes the processor to generate a third command signal that commands deflection of the azimuth gimbal based on the measured acceleration of the azimuth gimbal and the second command signal.
The computer program according to claim 12. The computer program updates the acceleration instructing the processor to deflect the azimuth gimbal based on the deflection of the biaxial pointing device and the deflection of the azimuth gimbal in response to the third command signal Command generation,
The computer program according to claim 14. The computer program further causes the processor to convert acceleration of the azimuth gimbal into an azimuth gimbal angle in a reference frame of the movable platform, and to deflect deflection of the two-axis pointing device from the reference frame of the two-axis pointing device. Converting the deflection of the biaxial pointing device in a reference frame of a movable platform;
The computer program according to claim 12.

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